Surface of byway_

I am traveling this year wit my bicycle through England. So I want to create a maprendering for this journey.

I discovered

One the one hand byways seem to be a minor road and suitable for a bicycle with heavy luggage. On the other hand I used the overpass-API and I have the feeling, byways are mainly not suitable for bicycles with luggage.

What is the truth?

Hi Gugsz, you could find that a few Byways in the UK are suitable for cycling, but most will not be easy going, especially with heavy luggage attached.
You will find that many are just tracks through fields and wooded areas, like this:

I would advise planning to stay on paved roads, or specifically marked cycleways.

As it says on that page, the tag highway=byway is deprecated. So these sorts of paths/tracks should be tagged as highway=path or highway=footway or highway=track etc.
Byway can refer to a specific legal designation in England in Wales, ie a “byway open to all traffic” or a “restricted byway”. So this should be specified with the designation tag. These tell you what sort of vehicles are allowed to use it, both types of byways allow bicycles.

But it doesn’t tell you anything about the condition of the surface. It could be extremely muddy or rocky, you might struggle to get along with a mountain bike.
For how suitable it is for cycling, you will have to check other tags. eg surface tag. If the surface tag is paved or gravel or compacted, then it is probably passable on a bike. Also the tracktype tag. grade1 or grade2 are probably OK for cycling. Maybe also helpful to check the tags for sac_scale or mtb:scale or smoothness, though they are not used as much.